The present invention generally relates to composite type magnetic heads and manufacturing methods thereof, and more particularly to a composite type magnetic head which is designed to carry out magnetic recording and reproduction with a satisfactory efficiency and a method of manufacturing such a composite type magnetic head.
Generally, a magnetic head which carries out recording and reproduction of a signal with respect to a magnetic recording medium having a high coercive force such as a metal tape must have a high saturation flux density at the time of the recording and a high permeability at the time of the reproduction especially in the high frequency range in order to obtain a sufficient reproducing sensitivity. It is known that a magnetic head having a high saturation flux density is obtainable when a magnetic metal material such as Sendust (registered trademark) and amorphous metals is used to make the magnetic head. On the other hand, it is known that a magnetic head having a high permeability is obtainable when a magnetic ferrite is used to make the magnetic head.
However, in the case of the magnetic head made substantially from the magnetic metal material, it is possible to obtain a satisfactory recording characteristic, but the electrical resistance of the magnetic metal material is small at the time of the reproduction and the permeability accordingly decreases due to the eddy current. As a result, at the time of the reproduction, the deterioration in the permeability is notable especially in the high frequency range, and it is impossible to obtain a satisfactory reproducing characteristic. On the other hand, in the case of the magnetic head made substantially from the magnetic ferrite, it is possible to obtain a satisfactory reproducing characteristic but it is impossible to obtain a satisfactory recording characteristic.
Hence, in order to obtain both a satisfactory recording characteristic and a satisfactory reproducing characteristic, various kinds of composite type magnetic heads have been proposed. In the present specification, a "composite type magnetic head" refers to a magnetic head which is constructed from a magnetic metal material and a magnetic ferrite.
As a first kind of the conventional composite type magnetic head, there is a magnetic head comprising a pair of magnetic head core halves which are made of a magnetic ferrite, as will be described later on in the specification in conjunction with drawings. At a part of the magnetic head where a gap is formed, each magnetic head core half is narrowed to approximately the track width, and a film made of a magnetic metal material is formed on a tip end part of the narrowed part of the magnetic head core half. The pair of magnetic head core halves are bound together with a gap member interposed between the respective magnetic metal films. According to this first kind of the conventional magnetic head, the gap is formed by the magnetic metal films made of the magnetic metal material which makes it possible to obtain a high saturation flux density, but since the film thicknesses of the magnetic metal films are extremely small, the magnetic head at the time of the recording is used in a state near the magnetic saturation. For this reason, there is a disadvantage in that the recording characteristic is not improved notably. In addition, a boundary between the magnetic head core half and the magnetic metal film on the tip end part of the narrowed part of the magnetic head core half is parallel to the gap, and this boundary acts as a pseudo-gap. Hence, there is another disadvantage in that the recording and reproducing characteristics are deteriorated by the pseudo-gap.
On the other hand, as a second kind of the composite type magnetic head, there is a magnetic head also comprising a pair of magnetic head core halves made of a magnetic ferrite, as will be described later on in the specification in conjunction with the drawings, but wherein each magnetic head core half is narrowed to a width less than the track width at a part of the magnetic head where a gap is formed. A film made of a magnetic metal material is formed on an apex part and sloping surfaces of the narrowed part of the magnetic head core half. The pair of magnetic head core halves are bound together with a gap member interposed between the respective magnetic metal films which are formed on the apex parts of the narrowed parts. The magnetic metal films of this magnetic head when viewed from above a contact surface thereof which makes sliding contact with a magnetic recording medium (for example, a magnetic tape), form an approximate X-shape. According to this second kind of the conventional magnetic head, a boundary between the magnetic head core half and the magnetic metal film on the apex part of the narrowed part is not parallel to the gap, and the problem of the pseudo-gap will not occur. The surface of the magnetic metal film on the apex part of the narrowed part is not flat, and this surface is lapped and flattened before binding the pair of magnetic head core halves together. When the surface of the magnetic metal film is lapped, the track width changes, but it is extremely difficult to control the track width to a desired track width. Further, when the contact surface is lapped after the pair of magnetic head core halves are bound together so that the contact surface has a desired curve, the track width changes due to the lapping. As a result, it is extremely difficult to accurately obtain the desired track width. Moreover, since the track width changes when the lapping is performed, the productivity of this magnetic head is poor and the manufacturing cost thereof is high.